Apparatus and method for vaporization cooling of electrical machines



2 SHEETS-SHEET l T. DE KONING APPARATUS AND METHOD FOR VAPORIZATION COOLNG OF ELECTRICAL MACHINES July 22, 1952 Filed Dec.

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July 22, 1952 T. DE KONING 2,604,500

APPARATUS AND METHOD FOR VAPORIZATION COOLING OF ELECTRICAL MACHINES Filed Dec. 15, 1949 2 swims- Smm 2 42 45 l g s y e MQ Patented July 22, 1952 UNITED STATES PATENT OFFICE APPARATUS ANI) METHOD FOR VAPORIZA- TION COOLING 0F ELECTRICAL MACHINES Theodore de Koning, Philadelphia, Pa.

Application December 15, 1949, Serial N o. 133,030

(Cl. Fil- 252) 10 Claims. 1

This invention relates to cooling systems fol' electric motors and generators, and more particularly to systems for cooling machines of this type by means of a finely divided liquid spray.

Prior to the present invention two methods have been generally used to cool electric motors and generators. These-are air cooling and hydrogen cooling, and consist essentially of causing a stream of air or hydrogen to flow through the machine. There are several objectionable features in each of these cooling systems. For example, in air cooling a large supply of air is required necessitating the use of large and expensive tan or blower installations and the machine must be open to the atmosphere thus allowing dust and other particles to be drawn into the mechanism. Hydrogen cooling, on the other hand, is very expensive requiring much accessory equipment and skilled men to operate it.

In Vaporization cooling according to the present invention, water is supplied in the form of a spray .to the interior surfaces of the machine. The machine is maintained at a pressure substantially below atmospheric pressure thereby lowering the vaporization temperature of the liquid sufiiciently to cause it to be converted substantially instantaneously into the vapor state bythe adsorption of heat from the machine parts and thus cooling the machine.

Vaporization cooling provides a feasible solu- I.

tion 'fo-r the cooling of large electric machines of all types. For example, compared with air cooling the heat transfer coeicient is at least fifty times as` great while at full load only l/Sl of the weight and twenty to forty percent of the gaseous volume isv required land even less is required at partial loads. On the `other hand, the heat transfer coeicient in a vaporization cooling system is at least twenty-live times as great as the heat transfer coefiicient for hydrogen. Thus, even an Y overdimensioned condenser in the present system will bemuch smaller than the cooler of a hydrogen cooled machine. Moreover, in vaporization cooling by the present invention, air and all other undesirable materials can be removed from the vapor which is another advantage over hydrogen cooling. Also, a liquid can be cleaned much easier and better than a gas. Dust from the atmosphere, brushes, collectors, and commutatore is removed as sludge by a fluid filter. The vapor flow cleans the interior of the machine progressively and neither a scavenger gas nor a longr drying-out period is required.

With the foregoing in mind theprincipal object of the presentinvention is to provide a novel f' 2 closed circuit cooling system for electrical machinery in which a liquid spray may be used as the coolant.

Another object of the present invention is to provide a novel closed circuit cooling system for electric mot-ors or generators in which a relatively small amount of coolant is required.

Another object of the present invention is to provide a vapor cooling system for electrical machinery as set forth, embodying novel features of construction and operation which will maintain a low moisture content in the insulation.

Another object of this invention is to provide novel means for cooling electrical machinery that will produce an even temperature gradient along the axis of the machine.

Another object of this invention is to provide a novel closed circuit cooling system having the advantagesset forth and in which a common vapor space may be used for two or more machines.

A further object of this invention is to provide a novel closed circuit cooling system for electrical machines requiring a minimum of accessory equipment.

A still further object of the present invention is to provide a cooling system of the type described, having the advantages and characteristics set forth, which is of comparatively simplified construction, and entirely eiiicient and effective in operation and use.

These and other objects of the invention and the various features and details of the construction and operation thereof are hereinafter fully set forth and described with reference to the accompanying drawings, in which:

Fig. 1 is a schematic diagram of a vaporizaton cooling system made in accordance with the present invention applied to an electric motor;

Fig. 2 is a cross sectional view taken longitudinally through an electric motor embodying the present invention;

Figs. 3 and 4 are views similar to Fig. 1 showing modified forms of the present invention;

Fig. 5 is a cross sectional view of a turbine, a generator, and a motor embodying the present invention utilizing a common vapor space for a plurality of machines; and

Fig. 6 is a graph showing how the insulation resistance under predetermined conditions of la machine cooled by liquid vaporization compares to that of an air cooled mchine under such conditions.

According to the present invention a liquid spray is caused to impinge on the rotor and stator parts of an electric motor or generator for the purpose of cooling the machine. The machine is enclosed in a fluid-tight housing and the interior is maintained at a pressure substantially below the pressure existing outside the housing. The reduced pressure within the machine housing lowers the vaporization temperature of the liquid spray suiliciently with relation to the normal operating temperature of the machine parts so that as the liquid comes into contact with the parts of the machine and absorbs heat therefrom, it is caused to vaporize substantially instantaneously thereby cooling the machine. Means are provided for condensing and cooling the vapor, withdrawing the condensate from the machine and returning it to the cooling system. Means are also provided for adjustably controlling the temperature desired to be maintained in the electric motor or generator.

Bearing the foregoing in mind, the drawings illustrate several embodiments of the present invention, one of which is illustrated in Fig. l. Referring more speciiically to Fig. l, reference numeral I designates generally an electric machine comprising a stator I2 and rotor I3. Casing members I, I are provided and, in conjunction with the stator I2 of the machine, provide a fluid-tight housing for the machine, for example, as shown in Fig. l, although the entire machine including the stator may be completely enclosed in a casing IIa, for example, as shown in Fig. 2. The rotor I3 is mounted to rotate within the stator I2 on a shaft I4 which is supported by bearings I5 in the casing members The machine. I may be either a generator or a motor, there being no difference in the operation of the cooling system of the present invention, hereinafter described.

The coolant is injected or introduced into the housing II in the form-of a liquid spray, for example, water, and is caused to impinge upon the rotor and stator parts of the machine. Injection of the liquid may be accomplished, for example, by means of a series of hair tubes I6 which are schematically shown in Fig. l but in Fig. 2 extend through the stator I2 circumferentially and longitudinally of the rotor I3. Liquid is supplied to these hair tubes IS from a supply pipe |8. A nozzle (not shown) may be placed on the ends of the hair tubes to produce a nely diffused spray.

The vaporized liquid flows through the machine to a chamber I9 provided within the housing, for example, at one end thereof removed from the parts of the machine, and is there condensed by a condenser 23. The condenser may be of the water cooled type having associated therewith a pump 2l for circulating water or other coolant through the condenser 20. The condensate is collected and withdrawn from the machine I3 and through a lter 22 by a condensate pump 23. Particles of dirt or dust on any parts of the machine |0 which may be removed by the vapor passing through the machine will be collected in the condensate and removed lby the filter 22. The condensate is delivered to a tank 24 from which it is recirculated.

A pressure substantially below atmospheric pressure is maintained within the casing by means of a vacuum pump 2 I. The vacuum pump 2| is connected to a shaft 28 along with the circulating pump 2l and the condensate pump 23, and the assembly is driven by a motor 29. By virtue of the reduced pressure in the machine I0 the condensate pump 23, which also serves as an injection pump for the cooling liquid, may be of the positive displacement type so that injection of the liquid into the housing is independent of the pressure therein.

Suitable means are provided to control the temperature of the component parts of the machine |0. For this purpose a temperature responsive valve 25 is connected in the liquid line I8 and disposed in the interior of the machine |0 between the rotor I3 and the chamber I3. This temperature responsive valve 25 is constructed and adjusted to close at and below a predetermined temperature and to open above that temperature thus controlling the ilow of cooling liquid through the intake pipe I8 to the point of injection into the machine I0 in accordance with the temperature of the latter.

It is desirable to adjust the temperature responsive valve 25 so that it will operate to out off the ilow of liquid at a temperature at which the vapor is slightly superheated as it leaves the air gap 26. This condition prevents any condensate from forming on the component parts ofthe machine I0. For example, at 0.8 p. s. i. a. pressure existing in the housing I I, the vaporization temperature of the liquid spray is 94.8 F. and a vdesirable temperature setting for operation of the temperature responsive valve 25 is approximately 104 F. Again, at 1.8 p. s. i. a. pressure existing in the housing I I, the vaporization temperature is 118 F. and a desirable temperature setting for operation o the temperature responsive valve 25 is approximately 127 F.

The machine I0 is put into operation by turning a handle 30 which closes an air inlet valve 3| and the electric circuits to the machine I0 and the motor 29. The air inlet valve 3| preferably is of the rotary plug type having a stationary casing 32 and a plug 33 secured to the handle 30 in such a manner that when the handle 30 nis in one position the valve 3| is open and when said handle 30 is rotated 180 the valve 3| is closed. In the open position of the valve dry air is admitted-,through an air filter 34 to the interior of the casing to absorb and prevent condensation of any moisture that might be in the machine ID.

Secured to the plug 33 and rotatable therewith is a switch element 35. When the air inlet valve 3l is closed the switch element 35 likewise is closed to complete the circuit to a solenoid operated relay switch 36. The relay switch 36 completes the circuit to the machine I0 and operates a second relay switch 3'! which closes the circuit to the motor 29 which drives the pumps 2|, 23 and 21, respectively. The relay switches 36 and 31 are normally held in the open position by means of springs 38 and 39, respectively.

An important feature of the present invention is the fact that the resistance of the insulation to current flow therethrough is substantially increased by the use of vaporization cooling. The electric disruptive strength of water is about twice that of air, and hence in the mist stage and especially in the superheated vapor stage water is a good insulator. With the machine in service water cannot penetrate the insulation as its surface is above the vaporization temperature of the liquid, and when out of service air admitted to the machine through the valve r3| and lter 34 also maintains the insulation dry. In air cooled or hydrogen cooled machines water on the windings can cause damage because of through wetting.

As shown in Fig..v 6 by the resistance-temperature;curve. for hygroscopicpaper insulation, there is. a vdrop in the resistance between 50 and' laodegrees centi.- grade for an air cooledttmachina;Whereas ina vaporlzation cooled machine.l the drop in'resistfA ance: is near the lowesttemperature the. machine will assume in. or outrof service, andasthevtem-r perature reaches.r the point. ,that thefmachine. will assume'i'in service theinsulation resistance increases. The reason ifor this is that4r any moisture lentrained inthe insulation will vaporize due `to vthe low pressure. in; the. machine and thus aid in increasing "the insulation! resistance.

Av4 more complete disclosure' of control equipment for the present invention is shown inithe modication in Fig. 3. In vthisfinstance thetemperature and pressure in. the interior of the. machine casing is controlled. byY temperature'and pressure'responsive means 42 and 43,` respectively, which inturnf actuaterheostats 44 vand 45 that control'the.- speed of a `motor. 29a. By this construction andY arrangement, as thek temperature within the casingincreases thetemperature responsive means 42' will operate to' decrease the resistance of' the'rheostat' 44 thus' increasing the current to a solenoid coil 46. This increases the pressure of the solenoid core 41.v against a carbon pile regulator 48 which in turn increases thev speedy of theV motor 29a thus increasing the rate of injection ofy cooling liquid into they machine ma. The'solenoid core 41 is normally held' away fromthe carbonipile regulator 48 by a'spring4'9. As. the pressure in the interior' of the machine' ma' increases the current to the solenoid. coil 50 likewise is increased through the action of the pressure responsive means 43 Aand the'rheostat-45- This increases the pressure of the solenoid'coretl on the carbon pile 48 thus increasing the speed ofthe mo` tor 29a and hence thev amount of liquid supplied to the machine. It will be noted that the pressure and temperature in the motori-Da are inter-related so that therel is no possibility of the two coilsv 46"and 5) opposing each other.

The condensate pump 23a also serves'as an injection pump. In this instance the condensate pump 23a is of the positive displacement' type having separate plungers 5| operated'by a crankshaft 52. The p'lu-ngcrs 5|"draw the condensate from a sump 5'3`in the motor casing ||cr and recirculate it through thev pipes |8a and injector tubes |6a.

The liquid level the condensate 'sum-p 53 remains practically constant under normal operating conditions. However, if a leak should occur in the injection system. the liquid level in the condensate sump 53 vwould drop rapidly indicatingthat not enough cooling liquid'was being supplied to the machine. Conversely, if too muchk liquid is supplied to the machine, the liquid level in the sump 513 would rise and there is the danger that the liquid would cause a short circuit in the windings. To prevent this, visible means are provided to give warning when these conditions exist. v K

Such indicator means may consist of aoat 54 having an extension 55 thereon which'operates to close contacts 55 when the 'iluid level rises above an upper safe limit and close contacts 51 when the level falls below the lower safe limit, respectively. When either of the contacts 56 or 51 is closed, an electric circuit to the signaling means, such as a lamp 53, is completed.

A further modication of the present invention is` shown in Fig. 4. In this embodiment an air 6. duct. isv provided i for condensing the vapor. The air-'..ductY 59v consists of a large tube 60 havingflared inletf and-outlet portions 6| and -62,-respec. tively',v to provide `substantially ay Venturi type section..y A motor drivenv fan '63 is supportedby afbracket E4 in the inlet of the air duct 59 to provide thefrequired. flowof; air therethrough. In operation,l the vapor" is withdrawn Vfrom the machine [0b through-an. outlet pipev 65 toa heat transfer unit66. placed in the air duct 59, land Y`a lfunnel-like collectorG'I-located in the interior ofthe machine lbtdirects they vapor into the pipe'. The condensate is removed from the heat transfer unit 6B by a condensate pump 232i andis collected; ina tank 2,417 from which it is. recirculated to the lmachine through pipe |8b andvtubesl'b. A float 54h may be positioned in the.v tank 2417130- operate a switch S similar to the type shown inFig.; 3 for the purposeA of. giving. a warning through rsome suitable signaling means 1' (not shownlffof an abnormal change in the fluid level in the tank 24h.

The' stator. |2b may vbe cooled additionally by tubes T0 containing a coolant,for example, a liquid such as water. The liquid in the pipes 'l0 after absorbing heat-'from the stator |2b is cooled by a heat transfer unitGS placed'in the `air duct 59', and then recirculated.

A furtherV modification.v o tthe present invention is shown in Fig. 5. 'In this instance'a tur-- bine Hand a generator Hic are connected together in axial alignment and have associated therewith a motor |0d. The turbo-generator and motor are arranged andinterconnected by means of a housing member .l2v which provides between them a common vapor space lc. Thus the cooling vapor from the motorld and the generator Isllc' may exhaust into the chamber'wc as. may the steam from the turbine 7|. By;this construction only a ksingle condenser is required for condensing the vaporized cooling liquid introduced to the generator Inc and motor. llldysince thev vapor from both of these machines lenters the common chamber .from which it passes through .a duct T3 to afcondenser (not shown).

From; the foregoingl it apparent that the present invention provides fa novel coolingv system for electric machines that is simple yet highly eillcient and effective in operation. Furthermore, a readily obtainable and comparatively inexpensive cooling liquidfmay be used to maintain the machine at a constant temperature with a minimumA of accessory equipment.

While certain embodiments of this invention have been illustrated and described herein, it is not intended to limit the invention to suchdisclosures, and changes and modifications may be incorporated and embodiedtherein within the scope of the following claims.

I' claim: n fl. In apparatus forcooling electrical machin` ery havingrotor and stator parts, a substantially huid-tight housing enclosing said parts, means providing a condensing. chamber relatively removed from they rotor and. stator parts, means .including a plurality of. small tubes for injecting a liquid spray interiorly of saidhousing into close proximity with the rotor and stator parts,V regu-. latine means to control. the'ow of cooling liquid to said tubes, mechanism operable to maintain a pressure within said housing substantially below thatl existing exteriorly of the housing, the reduced pressure in the housing operating to lower the vaporization temperature of the liquid spray sufficiently with relation to 'the temperatureoiv the rotor and stator parts of the machine to cause the liquid to be converted substantially instantaneously into the vapor state thereby absorbing heat from said parts and cooling the same, condensing means in said condensing chamber operable to condense the vaporized liquid, means responsive to the temperature of the vaporized liquid entering the condensing chamber operable to actuate said regulating means and thereby control the volume of cooling liquid injected into the machine through said tubes, and means including a pump for removing the condensate and recirculating the same to said machine.

2. In apparatus for cooling electrical machinery having rotor and stator parts, a substantially iiuid-tight housing enclosing said parts, means providing a condensing chamber relatively removed from the rotor and stator parts, a plurality of small tubes in said stator arranged circumferentially 'and longitudinally of the rotor parts for injecting a liquid spray interiorly of said housing and into close proximity with the parts of the machine, regulating means to control the flow of cooling liquid to said tubes, Amech- L anism operable to maintain a pressure within said housing substantially below that existing exteriorly of the housing, the reduced pressure in the housing operating to lower the vaporization temperature of the liquid spray suiciently with relation to the temperature of the rotor and stator parts of the machine to 'cause the liquid to be converted substantially instantaneously into the vapor state thereby absorbing heat from said parts and cooling the same, condensing means in f said condensing chamber operable to'condense the vaporized liquid, means responsive to the temperature and pressure of the vaporized liquid entering the condensing chamber operable to actuate said regulating means and thereby control the volume of cooling liquid injected into the machine through said tubes and means for removing the condensate and recirculating the same to said machine.

3. In apparatus for cooling electrical machinery having rotor and stator parts, a substantially fluid-tight housing enclosing said parts, means providing a condensing chamber relatively removed from the rotor and stator parts, a plurality of small tubes in said stator arranged circumferentially and longitudinally of the rotor parts for injecting a liquid spray interiorly of said housing and into close proximity with the parts of the machine, regulating means to control the now of cooling liquid to said tubes, mechanism to maintain the vaporization temperature of the liquid spray sufliciently lower than the temperature oi' the rotor and stator parts of the machine to cause the liquid to be converted substantially instantaneously into the vapor state thereby absorbing heat from said parts and cooling the same, said mechanism comprising means responsive to the temperature f the vaporized liquid entering the condensing chamber operable to actuate said regulating means and therebyv control the volume of cooling liquid injected into the machine through said tubes, and condensing means in said condensing .chamber operable to condense the vaporized liquid.

4. In apparatus for cooling electrical machinery having rotor and stator parts, a substantially fluid-tight housing, means for injecting a liquid spray interiorly of said housing and into close proximity with the rotor and stator parts of the machine, mechanism operable inc maintain a pressure within said housing substantially below that existing exteriorly of the housing, the reduced pressure in the housing operating to lower the vaporization temperature of the liquid spray suilcientlyv with relation to the temperature of the vrotor and vstator parts of the machine to cause the liquid to be converted substantially instantaneously into the vapor state thereby absorbing heat from said parts and cooling the same, means responsive to the temperature interiorly of the machine for controlling the flow of cooling liquid to the machine and the vaporization temperature thereof and thus the temperature interiorly of the machine, and means operable to remove the vaporzed liquid from the interior of said machine.

5. In apparatus for cooling electrical machinery having rotor and stator parts, a substantially huid-tight housing providing a condensing chamber relatively removed from the machine, means for injecting a liquid spray interiorly of said housing and into contact with the rotor and stator parts of the machine, mechanism operable to maintain a pressure within said housing substantially below that existing exteriorly of the housing, the reduced pressure in the housing operating to lower the vaporization temperature of the liquid spray sufficiently with relation to the temperature or the rotor and stator parts of the machine to cause the liquid to be converted substantially instantaneously into the vapor state thereby absorbing heat from said parts and cooling the same, a valve responsive to the temperature of the rotor and stator parts placed intermediate said parts and the condensing chamber for controlling the flow of cooling liquid to the machine and the temperature thereof, condensing means in said housing chamber operable to condense the vaporized liquid, and means for removing the condensate and recirculating the same to said machine.

6. In apparatus for cooling electrical machinery having rotor and stator parts, a substantially fluid-tight housing providing a condensing chamber relatively removed from the machine, means for injecting a liquid spray interiorly of said housing and into contact with the rotor and stator parts of the machine, mechanism operablel to maintain a pressure within said housing substantially below that existing exteriorly of the housing, the reduced pressure in the housing operating to lower the vaporization temperature of the liquid spray suiciently with relation tothe temperature of the rotor and stator parts of the machine to cause the liquid to be converted substantially instantaneously into the vapor state thereby absorbing heat from said parts and cooling the same, control means responsive to the temperature and pressure in the housing operable to regulate the flow of cooling liquid to the machine'and the temperature and pressure thereof, condensing means in said housing chamber operable to condense the vaporized liquid, and means for removing the condensate anl recirculating the same to said machine.

'7. In apparatus for cooling electrical machinery having rotor and stator parts, a switch for placing the machine in and out of service, a substantially fluid-tight housing providing a condensing chamber relatively removed from the machine, means for injecting a liquid spray interiorly of said housing and into contact with the rotor and stator parts of the machine, mechanism operable to maintain a pressure within said, Ahousingv substantially below that existingv exteriorly of the housing, the reduced pressure in the housing operating to lower the vaporization temperature of the liquid spray sufficiently with relation to the temperature of the rotor and stator parts of the machine to cause the liquid to be converted substantially instantaneously into the vapor state thereby absorbing heat from said parts and cooling the same, valve means operable to admit dry air to the interior of the housing when said machine is out of service, the switch operatively associated with said valve means and arranged to be in the open Circuit position when the valve is in the position admitting air to the interior of the housing and in closed circuit position when the valve is closed, condensing means in said housing chamber operable to condense the vaporized liquid, and means for removing the condensate and recirculating the Same to said machine.

8. In apparatus for cooling electrical machinery having rotor and stator parts, a substantially fluid-tight housing, mechanism including means defining a plurality of openings extending interiorly of the machine to inject a nely divided spray of cooling liquid into the air gap between the rotor and stator parts and into close proximity with said parts, regulating means to control the flow of cooling liquid to said plurality of openings, and mechanism to maintain the vaporization temperature of the liquid spray sufficiently lower than the temperature of the rotor and stator parts of the machine to cause all of the liquid to be converted substantially instantaneously into the vapor state thereby absorbing heat from said parts and cooling the same, said mechanism including means responsive to the temperature of the vaporized liquid operable to actuate said regulating means and thereby control the volume of the cooling liquid injected into said air gap through said openings.

9. In apparatus for cooling electrical machinery having rotor and stator parts, a substantially huid-tight housing enclosing said parts, means providing a condensing chamber relatively removed from the rotor and stator parts, means including a plurality of small tubes extending interiorly of the machine to inject a nely divided liquid spray into the air gap between the rotor and stator parts and in close proximity with said parts, regulating means to control the ilow of cooling liquid to said tubes, mechanism to maintain the vaporization temperature of the liquid spray sufficiently lower than the temperature of the rotor and stator parts to cause all the liquid to be converted substantially instantaneously into the vapor state thereby absorbing heat from said parts and cooling the same, said mechanism including means responsive to the temperature of the vaporized liquid entering the condensing chamber operable to actuate and regulating means and thereby control the volume of cooling liquid injected into said air gap through said tubes, condensing means in said condensing chamber operable to condense the vaporized liquid, and means including a pump for removing the condensate and recirculating the same to said machine.

10. In apparatus for cooling electrical machinery having rotor and stator parts, means including a plurality of small tubes extending through the stator parts to inject a nely divided liquid spray into the air gap between the rotor and stator parts in close proximity with said parts, regulating means to control the volume of liquid injected into said air gap through said tubes, mechanism operable to maintain a pressure Within said housing substantially below that existing exteriorly of the housing, the reduced pressure in the housing operating to lower the vaporization temperature of the liquid spray suciently with relation to the temperature of the rotor and stator parts of the machine to cause all of the liquid to be converted substantially instantaneously into the vapor state thereby absorbing heat from said parts and cooling the same, and means responsive to the temperature of the vaporized liquid operable to actuate said regulating means and thereby control the volume of cooling liquid injected into said air gap through said tubes.

THEODORE DE KONING.

REFERENCES CITED The following references are of record in the le of this patent:

UNITED STATES PATENTS Number Name Date 270,518 Vander Weyde Jan. 9, 1893 1,121,014 Hobart Dec. 15, 1914 1,190,048 Treitel July 4, 1916 1,761,387 Gay June 3, 1930 1,938,077 Lysholm Dec. 5, 1933 FOREIGN PATENTS Number Country Date 165,806 Great Britain July 11, 1921 170,946 Great Britain Oct. 31, 1921 

